1. Field
The present disclosure relates to an RFID tag capable of communicating with an external source, and an RFID tag communication apparatus capable of transmitting and receiving information by wireless communication.
2. Description of the Related Art
In general, it has been known that the reliability of wireless communication can be improved by using a frequency (=resonance frequency) best suited to the frequency characteristics of the antenna used in the wireless communication. Use of such frequency is particularly effective in cases where there is a long communication distance. An RFID tag communication apparatus that performs communication with an RFID tag and takes into consideration resonance frequency such as described above is presented in JP, A, 2000-148932, for example.
In this prior art, when the RFID tag communication apparatus is brought near an RFID tag and communication is performed, the inductance of the apparatus antenna of the RFID tag communication apparatus increases due to mutual induction with the tag antenna of the RFID tag. The resonance frequency of the apparatus antenna is therefore set to a low value in advance with the amount of this increase in mind.
In recent years, increased use of RFID tags has resulted in a wide variety of RFID tag applications and, in turn, a wide variety of forms of use of RFID tag communication apparatuses that perform communication with RFID tags in accordance with these applications. For example, needs such as the need to install an RFID tag communication apparatus on an installation surface made of metal, such as a steel desk, PC rack, or metal rack or shelf, and use the installed apparatus in an office or the home continue to emerge.
Nevertheless, in a case where the RFID tag communication apparatus is provided on a metal installation surface such as described above, the resonance frequency of the apparatus antenna is affected by the metal and therefore fluctuates. Conversely, in a case where the RFID tag communication apparatus is provided on a non-metal installation surface, there is no such effect and the resonance frequency does not fluctuate. Thus, when relatively good communication efficiency is desired in either case under the premise of such resonance frequency fluctuation, some type of device is needed to set the proper resonance frequency of the apparatus antenna (to set the resonance frequency with the RFID tag communication apparatus established as a single unit not placed on a metal installation surface or a non-metal installation surface).
In the above-described prior art, the fluctuation of such resonance frequency related to a metal installation surface and non-metal installation surface was not particularly taken into consideration.